That ideas has been echoed by research conducted at the Exercise Physiology Laboratory at Purdue University, which found that this form of high intensity training increases post-exercise energy expenditure through increased metabolism in Post Exercise Oxygen Consumption (EPOC).

This “after burning” effect on calories (and fat) works because the oxygen requirements of exercise were not met during high intensity training. It means that when you’ve finished at the gym and are sitting at home, there are millions of physiological reactions occurring in the body requiring calories, hence the increased metabolism.